[PATCH 9/9] migration/ram: calculate un/encoded_size only when needed.

[Mao Zhongyi]

Signed-off-by: Mao Zhongyi <maozhongyi@cmss.chinamobile.com>
---
 migration/ram.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index 41cc530d9d..ca20030b64 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -910,14 +910,15 @@ static void migration_update_rates(RAMState *rs, int64_t 
end_time)
         xbzrle_counters.cache_miss_rate = (double)(xbzrle_counters.cache_miss -
             rs->xbzrle_cache_miss_prev) / page_count;
         rs->xbzrle_cache_miss_prev = xbzrle_counters.cache_miss;
-        unencoded_size = (xbzrle_counters.pages - rs->xbzrle_pages_prev) *
-                         TARGET_PAGE_SIZE;
-        encoded_size = xbzrle_counters.bytes - rs->xbzrle_bytes_prev;
         if (xbzrle_counters.pages == rs->xbzrle_pages_prev) {
             xbzrle_counters.encoding_rate = 0;
-        } else if (!encoded_size) {
+        } else if (xbzrle_counters.bytes == rs->xbzrle_bytes_prev) {
             xbzrle_counters.encoding_rate = UINT64_MAX;
         } else {
+            unencoded_size = (xbzrle_counters.pages - rs->xbzrle_pages_prev) *
+                             TARGET_PAGE_SIZE;
+            encoded_size = xbzrle_counters.bytes - rs->xbzrle_bytes_prev;
+
             xbzrle_counters.encoding_rate = unencoded_size / encoded_size;
         }
         rs->xbzrle_pages_prev = xbzrle_counters.pages;
-- 
2.17.1